It is now well established that there is an inverse relationship between plasma high density lipoprotein (HDL) levels and coronary heart disease. The present research proposal focuses on the role of dietary factors which influence HDL composition, structure, metabolism and function. The studies will be carried out in a Clinical Research Center under controlled conditions in normal subjects and subjects with familial hypertriglyceredemia. The diets will include variations in carbohydrate, fat, (saturates and polyunsaturates) cholesterol will remain constant. HDL structure, composition, interaction with cells, and interaction with very low density lipoprotein and chylomicron remnants as it relates to lipoprotein lipase will be studied. The methods include standardized procedures for quantitation of lipoproteins, lipids, apoproteins and techniques of protein chemistry, immunology, physical chemistry and enzymology. Knowledge of HDL structure and composition should lead to a better understanding of HDL function and its relationship to coronary heart disease.